Aggressive and impulsive behaviour are common in Alzheimer's dementia. Therapy of these disorders is an important but difficult practical question. Aim. The purpose of this study was to determine the effect of pharmacological treatment of aggressive behaviour, while taking into account the dynamics of disease progression during observation. In the assessment of treatment acetylcholinesterase inhibitors (IAChE), valproic acid (VA), and antipsychotics were considered. Method. The study was based on a two-year naturalistic observation of nursing homes' residents with a diagnosis of possible Alzheimer's disease (NINCDS/ADRDA criteria) in its mild and moderate stage (at least 12 points in MMSE). Aggressive behaviour was measured by Cohen-Mansfield Agitation Inventory (CMAI), and the severity of dementia by ADAS Cog. Examination was performed twice: at baseline (0) and after two years of observation (2). All treatment administered during this time has been taken into account. 71 people diagnosed with Alzheimer's disease were enrolled to the observation. The average age was 77.10 (SD=8.39), the level of cognitive impairment by ADAS-Cog=20.40 points (SD=5.24). The second examination was conducted in 43 individuals. Results. In the group treated with IAChE there was a lesser increase of aggressive and impulsive behaviour in comparison to other persons. The differences between the examination (2) and (0) for the CMAI global scale were, respectively, 2.76 and 9.09 points. Similar results were obtained for subjects treated with VA (1.0 and 8.65). Antipsychotic drugs revealed a similar correlation (3.0 and 8.65), but this has not proven statistically relevant, while in the group treated with antipsychotics a significantly greater progression of dementia was observed. Conclusion. Acetylcholinesterase inhibitors may have beneficial effects on aggressive behaviour in the course of Alzheimer's Disease, similar to that seen with the use of valproic acid and antipsychotics.